The phrase "the whole is more than the sum of its parts" is not a bumpersticker slogan. Its an accurate assessment of a world in which many phenomena (including us) are emergent, always exceeding the sum of our parts. — Bitter Crank
The claim for ontological emergence is my prime target. As you pointed correctly the phrase "the whole is more than the sum of its parts" is an essence and roots of the theory of emergence. It is why to defeat this theory I need to start with its roots.
Another example. A rich delicious soup has a fixed list of ingredients. Eat the raw ingredients ground up together and it won't taste very good. Simmered in a pot for several hours, and it's heavenly. Flavors emerge in the soup that weren't there in the "un-stewed" parts. — Bitter Crank
You are right that taste of delicious soup is better (more) than taste of its ingredients. However you are right for the wrong reason, because you just forgot to include in your "equation" SOMEONE who tastes the soup. By adding this SOMEONE to your "equation" you may find the whole is now could be "more", "equal", or "less" that the "sum" of its parts, depending on the subjective taste of this SOMEONE. For example, I personally don't like Cesar salad (whole), but prefer its components (fresh vegetable) instead.
Your example with taste is a typical rhetorical example of emergence and is usually goes like that:
"Taste of sugar, a system phenomenon, could not be found in the carbon, hydrogen, and oxygen atoms that constitute components of sugar molecules". This example, limits the whole to sugar only while the another crucial element of the system is missing; SOMEONE who tastes the sugar and declares its taste vs. the taste of its component. Indeed for this SOMEONE taste of sugar and its purified components causes a very different taste (sensation perceived in the mouth and throat on contact with a substance). However to answer why it is different we don't need to invoke emergence; biochemistry and biology should be enough.
In the majority of examples, upon which the system approach is based, there is an exclusion of the invisible SOMEONE who designs, put together, tastes, or observes. Without this SOMEONE, the system property, like the taste, would not exist at all.
Omitting the creator or user of the system is the far most common mistake in emergentism. For example, a complex computer is built from the simple semiconductor components and it seems that the ‘computational intelligence’ of the computer is a new emerging phenomenon, because it cannot be found in its parts. However, the complexity of the computer is also due to the property (complexity) of human intelligence, which is not seen while we are observing the computer. Therefore, human intelligence is also one of the system’s causal powers and his or her properties determine the complexity of the semiconductor components, the complex wiring of the logic diagram, and sophisticated algorithms. In other words, there are no emerging properties in this example and
the properties of a computer could be reduced to the properties of its elements, including the creators of this computer.